WO2004065764A2

WO2004065764A2 - Device for actuating the gas exchange valves in reciprocating engines

Info

Publication number: WO2004065764A2
Application number: PCT/EP2004/000035
Authority: WO
Inventors: Helmut Schön; Kai-Uwe Keller
Original assignee: Thyssenkrupp Automotive Ag
Priority date: 2003-01-22
Filing date: 2004-01-07
Publication date: 2004-08-05
Also published as: EP1588029A2; ATE326618T1; WO2004065764A3; DE502004000589D1; DE10302260A1; EP1588029B1; DE10302260B4; US20060130786A1

Abstract

Disclosed is a device for actuating the gas exchange valves in reciprocating engines, comprising a housing (G), a cam (N) which is rotatably mounted in a rotating joint (ng) located inside the housing and the rotary movement of which is derived from a crankshaft, an intermediate member (Z) that is actuated by said cam via a first cam joint (zn), and an output member (A) which transfers said movement to the valve (V) and is effectively connected in a direct manner or via additional transferring members to the intermediate member. Another cam joint (za) which is formed by a curve on one of the two driving members forming the cam joint per se, is provided within the effective connection between the first cam joint and the output member. The shape of said curve encompasses at least one point of inflection (W) in the contact area in which the valve has a valve lift that is greater than zero.

Description

Device for actuating the charge exchange valves in reciprocating engines

description

The invention relates to a device for actuating the charge exchange valves in reciprocating piston engines, comprising a housing, a cam rotatably mounted in a swivel joint in the housing, the rotational movement of which is derived from a crankshaft, an intermediate member actuated by this cam via a first cam joint and an output member, which transmits the movement to the valve and is operatively connected to the intermediate member directly or via further transmission members and at least one further cam joint is provided within the operative connection from the first cam joint to the actuating member.

DE-A 101 00 173 describes a fully variable mechanical valve train for a piston internal combustion engine, with a drive means for generating a lifting movement acting against the force of a closing spring on the charge exchange valve and with an intermediate element arranged between the drive means, for example a cam, and the charge exchange valve, which acts on the charge exchange valve in the direction of its axis of movement and whose stroke path can be changed in the direction of the axis of movement via an adjustable guide element.

DE-A 100 06 018 describes a variable valve train for load control of a spark ignition internal combustion engine. The valve train is formed from a cam of a camshaft and at least one Inlet valve with a direct valve actuator, the output member, a transmission member and an adjusting means for influencing the lifting function of the transmission member. The transmission member is installed between the cam and the output member and has a first, acted upon by the cam and a second surface acting on the output member.

In the prior art there are a large number of mechanically variable valve gears for the control or load control of reciprocating engines. The publications cited above are therefore only to be regarded as examples. A common feature of the systems mentioned is that the rotational movement of the cam of a camshaft transmits a stroke movement to the charge exchange valve via the further transmission members of the valve transmission. The resulting elevation curve of these charge exchange valves can be changed during operation by relocating at least one of the transmission members located in the power flow. Both the valve lift and the valve opening angle are changed. So that the shift can be realized, at least one gear element is inserted between the driving cam and the output element that actuates the charge exchange control valve in the valve gears mentioned. This creates at least one additional degree of freedom in the movement, so that the desired shift is possible.

There are variable valve gears that consist of 4, 5, 6 or more gear links. The cheapest and simplest are the 4-link variable valve gears. As the number of transmission links increases, the complexity of the systems increases. The teaching according to the invention is therefore preferably applied to 4- or 5-membered systems, although the teaching can also be used for 6- and multi-membered systems. The power and torque transmission between the links of the valve train takes place via cam, thrust and rotary joints. The moving gear links are supported directly or indirectly in the housing. The stroke movement of the valve is adjusted, for example, by displacing joints or slide tracks in the housing, on which gear elements located in the power flow are supported.

Important criteria of such valve gears are that with the change in the valve stroke, the opening angle, i.e. the duration of the valve lock is changed and that the contact between the cam and the intermediate link is constantly maintained.

Furthermore, the accelerations of the valve when opening the valve should be as large as possible. The position and contours of the engaged cam joints as well as the position of the various rotary and thrust joints of the individual transmission links serve as influencing variables for this.

In valve drives of this type, the forces are strongly speed-dependent. The spring forces of the valve gear are designed so that the forces resulting from the acceleration at the highest speed for which the system is designed do not lead to loss of contact in the cam joints of the valve gear.

In the locking area of the valve, the forces introduced by the valve into the valve gear are zero. The control area of the valve can be divided into the area in which the greatest valve acceleration takes place and the area in which the greatest valve lift takes place. The area in which the greatest valve acceleration occurs is immediately adjacent to the rest area. This area occurs at high engine speeds in a curve joint which is involved in a reciprocating transmission link, the greatest forces.

Systems of this type are designed for the transition from the rest area to the control area in such a way that the constraining forces occurring in this area are minimized.

In the further course of the valve lift, the area in which the greatest valve lift takes place follows. At high engine speeds, the forces drop here. In the prior art, however, the valve ratios change the angular relationships in the transmission such that even if the amounts of the forces introduced no longer increase, the resulting constraining forces can still increase.

Furthermore, it is often a considerable disadvantage in the prior art that the adjustment forces or adjustment torques are very high due to the selected curve shapes, so that disproportionately large forces are introduced into the transmission members involved.

As a consequence of the above-described disadvantages in the prior art, it may be necessary to achieve an undesirably strong design in order to achieve the specified service life, at least for individual transmission elements.

The invention has for its object to develop the device described in the generic part of claim 1 or claim 10 in such a way that the forces or moments between the transmission members, and if possible the forces or moments within the adjusting device, are minimized. This means that the constraining forces in the System are kept as low as possible, which advantageously leads to a reduction in the frictional forces.

This object is achieved with a device having the features of patent claim 1 or of patent claim 10.

By designing the contours involved in the curve joint, the direction of force can be freely determined within certain limits. By inserting a turning point according to the invention into one of the contours involved, the curve joint is designed in such a way that the angle of the power line remains as constant as possible during the entire movement sequence. As a result, the change in the amount of the force introduced is kept as small as possible.

Investigations have shown that the insertion of a turning point is only necessary at a contour point of the cam joint that is in contact with valve lifts that are larger than 0.5 mm. The range of the valve elevations from 2 mm to 7 mm is particularly preferred.

In the preferred range, the values of the valve acceleration are negative in the case of actuation of the largest possible valve lift curve, since the valve speed is braked. The greatest resulting constraining forces are to be expected here.

The effect of the invention is described below using the example of the design of the curved joint between intermediate link and output link with the contour according to the invention on the intermediate link. In the example, the output member is formed by a rocker arm or rocker arm.

The force introduced into the driven member is determined by the acceleration, friction and spring forces from that with the driven member operatively connected valve. These are determined by the design and the special design of the engine. The values depend on the engine speed and other influencing factors.

According to the normal at the momentary contact point of the cam joint between the output member and the intermediate member, a force is introduced into the intermediate member by the output member. The size of the force introduced into the intermediate member is determined by the ratio of the distances between the pivot point of the output member in the housing and the lines of action of the forces on the one hand to the intermediate member and on the other hand to the valve. The line of action of the force is the straight line, which is determined by the direction of the force and the position of the force. The directions of the forces thus essentially determine the force introduced into the intermediate member. If the direction of the force introduced into the intermediate member is perpendicular to the connecting line between the pivot point of the output member and the point of application of the force, the amount of the force introduced into the intermediate member is the smallest.

With the subject matter of the invention, the change in direction of the force is determined by a description of the direction of the surface normal at the contact point in this curve joint. To avoid the above-mentioned constraining forces, it is advantageous to make the surface normal at the contact point at which the greatest valve lift is achieved approximately equal to the surface normal at the contact point at which the greatest valve acceleration occurs. Such a change in direction can be implemented according to the invention by a turning point in one of the two curves of the curve joint concerned.

To maintain the specified valve lift curve, the contour on the cam is adapted accordingly, for example. The mechanism of action described above also applies when using a bucket tappet as an output member and is to be applied in an analogous manner.

Furthermore, the teaching according to the invention can also be applied to valve gears in which the cam joint designed according to the invention is arranged at a different location than described above. It is irrelevant whether the curve of a cam joint of the gear elements engaged is designed in this way or a curve in the housing on which one of the gear elements is supported in a cam joint.

Advantageous further developments of the subject matter of the invention can be found in the subclaims.

The object of the invention now provides a solution by means of which the forces or moments between the transmission members and, if possible, the forces or moments within the adjusting device are minimized. This means that the constraining forces in the system are kept as low as possible, which at the same time advantageously leads to a reduction in the frictional forces.

The subject of the invention is generally realizable in all cam joints in the valve transmission, with the exception of the cam joint in which the driving rotating cam is involved. The execution of the curve of the curve joint according to the invention on one of the transmission members involved acts on both transmission members forming this curve joint. It is therefore irrelevant on which of the two curves of the curve joint involved the embodiment according to the invention is arranged. In the preferred embodiment of the valve gear, the contour described in the subject matter of the invention is applied to one of the curves of the intermediate link. Both Curve joints of the intermediate link to the output link or to the housing can be selected.

In an advantageous development of the invention, in addition to the formation of a turning point in the area of the valve lift, the transition area from the rest area into the control area is specifically represented. This transition area plays an important role for both opening and closing the valve. While opening should take place as quickly as possible, the closing speed must be limited in its final phase in order to limit wear and noise. Since the same transition area between the rest area and the control area is run through for opening and closing the valve, the two opposite requirements must be met by a compromise. The immediate transition area between the rest and control areas is formed from route and involute sections.

The subject matter of the invention is illustrated using an exemplary embodiment in FIGS. 1 and 2 and is described as follows. Show it:

Figures 1 and 2 Different positions of a valve gear for variable actuation of the charge exchange valves in reciprocating engines.

Figures 1 and 2 show a device for actuating a charge exchange valve V in a reciprocating piston engine, not shown. The device includes a housing G, a cam N which is mounted so that it can rotate in a pivot joint ng in the housing G, the rotary movement of which is derived from a crankshaft (not shown). An intermediate member Z is actuated by this cam N via a first cam joint zn, which acts on an output member A, which transmits the movement to the valve V. Within the operative connection from the first cam joint zn to the output member A, a further cam joint za is provided, which is formed by the contours Kz on the intermediate member and Ka on the output member. The shape of the contour Kz on the intermediate element usually has exactly one in the transition between the area in which there is no valve lift - the area of keeping the valve closed - and the area in which there is a valve lift - the control area which is given when the valve is opened Turning point W2 on. Furthermore, the shape of the contour Kz on the intermediate member has an inflection point W in the contact area in which a valve lift that is greater than zero is generated. The turning point W is essentially in the area of the cam joint, which is to be assigned to the area of the beginning and the end valve stroke. As can be seen in particular from FIG. 2, the inflection point W is arranged in the region of the curve Kz describing the largest possible valve lift. In this example, the curve Ka is formed by a circular arc, although other geometric shapes are also conceivable. The cam joint za is arranged between the intermediate member Z and the output member A in this example.

Figure 1 essentially describes the area of valve closure keeping, i.e. Valve stroke s1 = zero, while FIG. 2 describes the control range which is given when valve V is opened, i.e. Valve stroke s2> zero.

In the examples, only a single intermediate member Z is provided. As described in the prior art, further transmission elements can of course also be provided, so that the same are also included in the scope of protection.

Claims

claims

1 . Device for actuating the charge exchange valves (V) in reciprocating piston engines, consisting of a housing (G), a cam (N) rotatably mounted in a swivel joint (ng) in the housing (G), the rotational movement of which is derived from a crankshaft, one of these Cam (N) via a first cam joint (zn) operated intermediate member (Z) and an output member (A), which transmits the movement to the valve (V) and is operatively connected to the intermediate member (Z) directly or via further transmission members and within the Active connection from the first cam joint (zn) to the output member (A) is provided, at least one further cam joint (za), characterized in that this further cam joint (za) on one of the two gear members (Z, A) forming the cam joint (za). is formed by a curve (Kz or Ka), the shape of which in the contact area in which the valve has a valve lift that is greater than zero, at least one turning point (W) au fweist.

2. Device according to claim 1, characterized in that the movement on the valve (V) can be changed by changing the position and the orientation of at least one gear member or its joint positions to the housing (G).

3. Device according to claim 1 or 2, characterized in that the cam joint (za) on one of the two gear members (Z, A) forming the same is formed by a curve (Kz or Ka), whose shape in the contact area in which the valve has a valve lift that is greater than zero, has an exact turning point (W).

4. Device according to one of claims 1 to 3, characterized in that the turning point (W) is arranged substantially in the region of the beginning and ending valve stroke.

5. Device according to one of claims 1 to 3, characterized in that the turning point (W) is arranged in the region of the curve describing the largest possible valve lift (Kz or Ka).

6. Device according to one of claims 1 to 5, characterized in that the cam joint (za) on the other of the two gear members (Z, A) forming the same is formed by a curve (Ka or Kz), the shape of which is a circular arc or is formed by a circle.

7. Device according to one of claims 1 to 6, characterized in that the cam joint (za) between the intermediate member (Z) and the output member (A) is arranged.

8. Device according to one of claims 1 to 6, characterized in that the cam joint (za) between the intermediate member (Z) and the housing (G) is arranged.

9. Device according to one of claims 1 to 6, characterized in that the cam joint (za) is arranged on a transmission member located between the intermediate member (Z) and the output member (A).

10. Device for actuating the charge exchange valves (V) in reciprocating piston engines, consisting of a housing (G), a cam (N) rotatably mounted in a swivel joint (ng) in the housing (G), the rotational movement of which is derived from a crankshaft, one of this cam (N) via a first cam joint (zn) operated intermediate member (Z) and an output member (A) which transmits the movement to the valve (V) and is operatively connected to the intermediate member (Z) directly or via further transmission members and within of the operative connection from the first cam joint (zn) to the output member (A), at least one further cam joint (za) is provided, characterized in that this further cam joint (za) on one of the two transmission members (Z, A ) is formed by a curve (Kz or Ka), the shape of which in the contact area, in which the transition from the area in which no valve lift is generated, to the area in which a valve lift is generated, by a distance and by an involute section is formed.